This invention relates generally to off-road motor vehicles, such as tractors, and more particularly, to a hydraulic clutch operatively connected to a transmission to control the output thereof.
Tractor transmissions are typically provided with a master clutch operatively connecting the output of the engine to the transmission. This master clutch can be modulated under full power from the engine to provide a limited transfer of operative power to the transmission, and therefore to the operatively connected drive wheels, through a process typically referred to as "inching". Modulation of the master clutch creates heat which must be accommodated to prevent destruction of the clutch. To cool the clutch, a high flow of lubricating oil can be passed through the clutch to dissipate the heat; however, a high oil flow is not desirable under normal operating conditions as the oil can be better utilized in other parts of the transmission lubrication circuit.
Accordingly, it would be desirable to provide a hydraulic circuit for the lubrication of a transmission and master clutch that will provide a high flow of oil through the clutch whenever the clutch is being modulated, but provides only a normal low oil flow whenever the clutch is disengaged or whenever the clutch is fully engaged and is not being modulated.